Arduino-HID-Remote

The Arduino library already has support for acting as keyboard or mouse, but not media control buttons like play/pause and volume control. This Arduino skectch is about the simplest way to add such functionality. (A USB-capable Arduino like the Leonardo is obviously required.) Other libraries provide more flexibility, but are also more complicated to use and may generate larger code. The file hid_remote.ino contains a fully working example, using a simple keyboard matrix. (The random-seeming row and column pin assignments are just because that's what routing I happened to use on my board.)

Due to the way the USB HID specifies how multimedia buttons works, support for them can't be trivially incorporated into a keyboard device. Instead, you have to add a new report and descriptor. Fortunately, at some point the Arduino USB library got rewritten to make doing that quite easy.

This code is inspired by this Stefan Jones blog post. However, his example predates the rewrite of the Arduino USB HID API, so I had to modify it to work with the new API. Ultimately, I ended up pretty much rewriting all the code completely. Even my descriptor is completely different.

Usage

Add the HIDRemote.h and HIDRemote.cpp files to you sketch folder and place #include "HIDRemote.h" at the top of your sketch.

In your setup() routine, add HIDRemote.begin(); at some point.

The actual API mirrors the usage of the Keyboard library. There are HIDRemote.press() and HIDRemote.release() routines to simulate pressing and releasing keys, as well as HIDRemote.releaseAll() and HIDRemote.pressAndRelease().

The following constants can be passed to press or release. Some or all of these may have no effect on your particular operating system or application. Note that they are 16-bit i.e. use uint16_t.

• HID_REMOTE_PLAY Play button; if media is already playing, should have no effect.
• HID_REMOTE_PAUSE Pause button; if no media is playing, should have no effect.
• HID_REMOTE_RECORD Record key, to start recording
• HID_REMOTE_FAST_FORWARD Fast-forward
• HID_REMOTE_REWIND Rewind
• HID_REMOTE_NEXT Skip to next track
• HID_REMOTE_PREVIOUS Skip to previous track
• HID_REMOTE_STOP Stop media playback
• HID_REMOTE_EJECT Eject media
• HID_REMOTE_RANDOM Select randomized track playback order
• HID_REMOTE_VOLUME_UP Increment volumne
• HID_REMOTE_VOLUME_DOWN Decrement volumne
• HID_REMOTE_SLEEP Enter sleep mode
• HID_REMOTE_REPEAT Activate track or playlist repeating
• HID_REMOTE_PLAY_PAUSE Play/pause button; if media playing, pause playback; if media is paused, resume playback
• HID_REMOTE_MUTE Mute/unmute volumne

You can change what buttons are available by changing the descriptor in HIDRemote.cpp. Remember to change the constants in HIDRemote.h to match.